In the normal human heart, the sinus node, that is generally located near the junction of the superior vena cava and the right atrium, constitutes the primary natural pacemaker initiating rhythmic electrical excitation of the heart chambers. Disruption of the heart's natural pacemaker and conduction system, as a result of aging and/or disease, can be successfully treated using various implantable cardiac stimulation devices, including pacemakers and implantable cardioverter defibrillators. A pacemaker is generally arranged to deliver rhythmic electrical pulses to the heart to maintain a normal rhythm in patients having bradycardia, which is too slow of heart rate, or other conduction abnormalities. In contrast, an implantable cardioverter defibrillator, commonly referred to as an “ICD”, can recognize tachycardia and/or fibrillation and deliver electrical therapy in order to terminate such arrhythmias. In addition, such ICDs may often be configured to perform pacemaking functions (or pacing) as well.
Depending upon patients' needs, the ICDs generate pacing, cardioverting, and/or defibrillating pulses, and deliver them to excitable cardiac tissues of the patients' heart through electrical leads and electrodes. Difficulties arise when one or more electronic components of the ICDs leak currents and dissipate energy. The leaky components drain electric power from the power cells of the ICDs, resulting in the generation of electrical shocks with voltages or currents less than those required to remedy the ailing hearts. The premature power depletion may cause early retirement of the ICDs. In addition, the controllers of the ICDs and other components may malfunction due to weak power supply, and may eventually lead to dangerous conditions.
The problematic components of the current ICDs include decoupling capacitors that are connected to the power cells. In general, these decoupling capacitors are connected in parallel with the power cells to provide a relatively constant current and voltage. However, the decoupling capacitors may not be as reliable as expected. Many times, such capacitors exhibit partial shorts, deplete the power cells, and significantly reduce the longevity of the ICDs.
The ICD may monitor the electric voltage or current to its components, in order to detect the current leakage. However, the measured voltage or current might not identify the source of such leakage, because conventional current meters measure only the electric current supplied to all the circuits of the ICD.
In addition, because the current leakage in an ICD is unpredictable, the ICD undergoes a long hold period after it is manufactured to measure the voltage of the power cells and to estimate the leakage current. Such a process is not only inconvenient but also uneconomical. Furthermore, such a process might not detect less severe current leakages in the decoupling capacitors.
Therefore, it would be desirable to provide a leakage detection and prevention system for use in an ICD, with the ability to readily detect current leakages and to prevent, or at least minimize, the leakage by, for example, isolating leaky electronic components from the power cells.